The invention relates to a feed-controlled core drill, in particular a pedestal-guided diamond core drill for reinforced concrete, and an associated control method.
When core drilling rock, ultra hard cutting edges or diamonds of the drill bit penetrated slightly into the substrate and carry it away. The high torque and feed pressures required for core drilling rock are usually applied against a machine pedestal, which is solidly connected with the substrate. If the control of the feed is effected manually by the operator using a lever wheel, a substrate-specific optimum penetration depth of the blades is not possible, by which early wear of the cutting edges results along with reduced drilling performance.
According to DE 19807899, an adaptive feed control for a pedestal-guided diamond core drilling machine is disclosed, which controls the feed using a PID controller depending on the current consumption of the electrical motor or a torque relative thereto. As a consequence of this type of power-based control, there is only one maximum torque available at a constant speed pre-defined by the gear reduction ratio. Changes in the substrate such as encountering reinforcement leads to non-optimum torque/speed-pairings.
In addition, as disclosed in U.S. Pat. No. 4,618,805, a drill machine has an electrical motor with a motor control, which can be pre-set to the motor characteristic curve of maximum power for different working points independent of each other and can be switched automatically between the working points.